Recover the data for the EDB measures of a master workbook from a previous backup.

If generate_index is true, this task will read a file called latest_backup.txt under backup_root, which should contain a single line with the timestamp of the latest backup. The task will then lookup backup-spec.proto under the directory backup_root/$timestamp, and will proceed loading the csv files in there.

If generate_index is false, then the backup_root folder itself will be used to lookup backup-spec.proto and the set of csv files.

@param app_prefix a URI path to construct the service URI. This is the prefix used when configuring workbook services (via lb:web:workbooks:config:app_prefix) or the modeler (via modeler_config:services:prefix:master). E.g. "my_project".

@param backup_root the location where the files to recover are stored. This should be a directory or cloud store location. If lookup_index is true, this should point to the directory that contains the index file; otherwise, this should point to the directory that contains the data and the backup specification. Avoid trailing slashes.

@param lookup_index whether the task should use the file in backup_root containing the timestamp of the latest backup. This is often generated by “lb.wb.BackupWorkbook”.

@param transport the transport used to execute service calls. This is used both to lookup the backup specification service as well as the dynamic TDX services exposed by the workbook framework.

@param async whether to use the asynchronous transaction protocol when importing the recovery data. This is highly recommended as it uses much fewer resources than the synchronous protocol.

@param poll_delay when using the asynchronous transaction protocol, the client will send all the specification of the files to import in a transaction and will then start polling until the transaction is over. This parameter determines the duration to wait between polls. Note that the client polls immediately after the commit requests returns, so short transactions may never need to wait.

@param txn_service the transaction service to use when importing the backup files. If not set, the default will be the concatenation of app_prefix and "/workbooks/txn", which is the prefix exposed by the workbook framework by default. A transaction service is always used, to ensure that a consistent snapshot is imported.

@param txn_timeout the timeout for the transaction that imports data, in seconds.